Balanced loom operation



Jan. 18, 1949. F. D. SNYDER BALANCED LOOM OPERATION Filed April 4, 1947 INVENTOR Frederick D. Snyder.

ATTORNEY NU-l Patented Jan. 18, 1 949 BALANCED LOOM OPERATION Frederick 13. Snyder, Milton, Mass, assignor to Westinghouse Electric Corporation, East Pittsburgh, Pa., a corporation of Pennsylvania Application April 4, 1947, Serial No. 739,414

'7 Claims. 1

My invention relates to motor control systems and more particularly to systems of control for Correlating the operation of a plurality of electric motors.

In many fields of industry, electric motors operate loads that have the characteristics of a greatly unbalanced flywheel. This is especially true in the textile industry. Usually a large number of looms are mounted on a single floor and each loom is operated by its own motor. If all the looms, or a great number of them, happen to get, in step, as happens from time to time, then the sum of all the unbalanced flywheel type loads is transmitted to the floor with the result that the building begins to oscillate. Usually buildings are not designed for such effects, but even if the building were designed for earthquakes, a quaking building does not appear to be a secure place to the personnel.

One broad object of my invention is to so correlate the operation of a plurality of motors, operating loads of the unbalanced flywheel type, that large vibrating stresses are not transmitted to the building.

A more specific object of my invention is to correlate the operation of a plurality of motors disposed on a single floor of a building into pairs such that the two motors comprising each pair are operated out-of-phase to thus balance the individual unbalanced loads in twos.

A somewhat broader object of my invention is the provision of operating two electric motors that an unbalanced load operated by one motor is always substantially 180 out-of-phase with the unbalanced load operated by the other motor. 1

Other objects and advantages will become more apparent from a study of this specification and the accompanying drawing, in which:

The single figure is a diagrammatic showing of my invention.

In the figure, two looms, I and 2, are illustrated graphically. Loom I has a crankshaft 3 with a crank 5 which crank is connected to the lever 1 of the lay by the link 9. The lever l of the lay is pivoted at l l. A motor Ml rotates the crankshaft 3 through a reduction gear, not shown, so as to oscillate the lever 1 back and forth at speeds such that the lever operating the lay makes from 120 to 220 complete cycles per minute, depending on the motor speed selected. Since the lay weighs a considerable amount, an appreciable vibratory force is set up in the floor supporting the loom. For various reasons, it is not feasible to counterbalance this crankshaft and'load.

In the figure, 2 represents a second loom. This loom is similar to the first, having the crankshaft 4, crank arm 6, link Ill, and the lever 8 for the lay pivoted at l2. The second loom is operated by motor M2. Normally the loom loads are about the same. The looms are driven by individual motors of the same frame size and capacity and are usually adjusted to operate at the same speed.

If a considerable number of the looms or, as may sometimes happen, all of the looms on the same floor happen to get into step, the total force transmitted to the supports becomes great enough to set up dangerous vibrations of the building. One of the purposes of my invention is thus to operate the looms in pairs, and to operate each pair such that the crankshaft of one loom is always out-of-phase with the crankshaft of the other. The out-of-phase relation may be such that one crankshaft is from 160 to 200 behind the other. To break up the unbalance effect of the picker stick, the extreme Values are preferable. In this manner, the forces of the two looms that operate as a pair neutralize each other. It thus makes little difference how the pairs operate with respect to each other since no concentrated force will be transmitted to the building floor. How I accomplish the novel result will become more apparent from the detailed description given hereinafter.

The starting and stopping of any two looms that are correlated, that is, combined during normal operation need not be interrelated. If loom l is to be started, the attendant actuates controller CI, whereupon the motor MI is energized from buses L, through controller Cl, the lead l3, contacts l5 and lead H, the lead I 9, contacts 2|, and lead 23, and lead 25. Energization of leads 23 and 25 energizes the relay 2'! to effect the closingof contacts 29.

If loom 2 is to be started, the controller C2 is actuated, whereupon circuits are established from buses L, through controller C2, the lead [4, contacts l6 and lead l8, the lead 20, contacts 22, contacts 22, and lead 24, and lead 26 to energized motor M2. The energization of leads 24 and 26 effects the energization of relay 28 to effect the closing of contacts 30. In the absence of the energization of the control circuits, the tWo looms I and 2 operate independently of each other exactly as is now the case with prior art practice.

To combine the operation of the two looms, I mount two cams 3| and 33 on the crankshaft 3. The cams act on limit switches 35 and 37, respectively. A similar pair of cams 32 and 34 are ated by cam34 close.

3 mounted on shaft 4. These two cams act on limit switches 36 and 38, respectively.

To gain an understanding of the sequence of operation of the limit switches 35, 36, 3'! and 38, I take the trailing edge of the raised portion 39 on cam 3i as the starting point and count angular measure in the clockwise direction, the direction of rotation of the shafts 3 and 4; for the moment consider that the shafts are so disposed that the crank arms 5 and 6 are exactly 180 out of phase.

The raised portion 39 extends from to 60 over the surface of the cam 3|. The cam 33 has a raised portion 45 whose trailing edge begins at 10 and extends over the cam surface to 120. The raised portion 40 on cam '32- extends from its trailing edge in the clockwise direction from 180 to 240. The raised portion 40 on-zcamfi l extends from 190 to 300.

This means for a 60 rotation, contacts 4i ar closed and for the remaining 300 contacts 43 are closed, and at the same-time, still assuming exact 180 out-of-phase operation of the two crank arms and 0, contacts 42 will be closed for the same 60 rotation; and then contacts 44 will be closed for the remaining 300 rotation. This also means that contacts 4? are closed for 110 beginn-ing fiW-ahead of the closure of contactsM and contacts 48 are closed for the same l-= rotation.

As long' a-s the crank armsare 180 out'of phase, the circuit, including-the contacts 4%, 30, 2-9, 41 and 4l-,-the-actuatmg coil ie-of the contactor 5| andcontac-ts 44, is on open circuit all the time. Similarly, the'c-ircuit including contacts 48, 30, 2'9, 4'! and 43-, actuating-coil 50 of contactor "5 2-, and contacts 42 is onopen-all the time. The contacts and-2l andthe contacts 16 and 22 are thus closed and the two motors MI and M2 will operate atfull voltage and thus full speed.

as indicated in the figure, loom 1 is ahead of loom 2', :say by as shown, then the time interval'of energi-Zation 1 of coil 49 is proportioned to the angle of lead. -Contactor 5i thus opens the contacts i5 and 2t to insert the resistors 53 and- 55 in the motor primary circuit. That the time interval ofenergizationof coil 49 is proportional to the angle of lead will become more apparent from-a study of the disposition of the cams in the figure. As cam 33" rotates in the direction-indicated with :the lead mentioned, contacts fi 'l will closeand-20 "1atercontacts 48 actu-- Since both of the ca-ms 33 and 34 actuate-theirrespec-tive limit switches 3"! andfifi to'closeol position, the contacts- 4-! and- 4-8 willbe closed at the same timeduringQO rotation. After contacts 41 are closed --for 60, contacts 4! are-=closed but at the same time, since shaft 4' lags by 200, contacts 44 are still closed and will remain closed till shaft 4 moves through 20. After the shaft "4 has turned through 20, contacts .44. will open. This is the condition shown in the figure. The showing is thus exactli at theend .of thecorrectioncycle. An instant later contacts t5. and .21 close and both motors again operate on full voltage.

While contacts 42- close at theend of the correction cycle,,,contacts 41 open 10 ahead of the closure of contacts 4.3. The coil 50 can thus not he energized.

The resistors53. and 55., as well as theacorresponding. resistors .54 land. 56. for motor M2, are

usually chosen .to have an appreciable resistance value so that insertion of .these resistors in the motor primary circuit will. very materially reduce the motor torque during the short period the contacts i5 and 2! are open. The resistors 53 and 55 and 54 and 56 may even be chosen to have infinite resistance value, that is, in some cases may not be used at all so that the operation of contactor 5| will open-circuit two motor armature leads for motor MI, and operation of contactor 52 will open-circuit two motor armature leads for motor M2.

If loom 2 leads loom I, then an energizing circuit for coil 50 long enough to actuate contactor 52 is established. Contacts l6 and 22 are thus opened to insert the resistors 54 and 56 in the primary circuit of motor M2. Motor M2 is thus slowed down to bring the two looms again back toout-oi-ph-ase operation.

From the foregoing it is apparent that the length of time the leading motor torque is decreased will depend on the amount of out-ofphase operation. This is important because the correcting effect is in proportion to the magnitude of the out-of-phase operation.

The relays 27 and'28' are a refinement; not an absolute necessity. These relays prevent closing of the control circuits shown except when both looms are in operation. These relays also permit unfailing starting of either motor when the other is at rest. For instance, if both looms should happen to be atrcst in the particular position shown and contacts .29 and 3;!) were replaced by solid leads then- .motor Ml could ,not'be started.

During starting no attention needb paid .to the relativepositionsof the. cranks/baits- Each motor is started independently. The motors-drift alon independently but .as soon as they get within less than 60 of the out-of phase.operation.for which the cams are adjusted, .the system captures the angular-position ofxthe shafituswitchingmeans op:- eratively related with the outpntshaft of the other motor iorclosing andzopening contacts as ,a function of- "the angular position .of. the second haf ,v said: switching irrearrs being so. :related to their resp ctive outputn shatts. that sSflid' control circuit is energized when the; shaftsere not out of phase, and means operable by the. control circuit for opening the motor armature circuit: :Oif themotor that is lcadingbymorethan asselected .out-Fof-phase value.

2. In :a system. off-control, in combination, a motor driving a load-.oflthe type: ot .a h y balanced flywheel, a. second =motor of: about the same capacity as the first motor driving the-same type ofload atabout the samesspced,synchronizing means, for so synchronizing said motors that when the unbalance-force. of onelpadzisuin one horizontal direction the unbalance force of the other loadwill be in the opposite horizontal-1direction, said synchronizing 11368111$1COH11D1T1Sjfig a controlcircuit, and, switches in the. circuit that y-nchronously :cIcSeonIyin response to the .direction of the unbalance forces that is other than out of phase, and means responsive to the energization of the control circuit for temporarily opening the motor armature circuit of the met 1 leading the other motor by more than the selected out-of-phase value.

3. In a system of control, in combine motor driving a load of the type of ah; i. balanced flywheel, a second motor of about L113 same capacity as the first motor driving the same type of load at about the same speed, synchronizing means for so synchronizing motors that when the unbalance force of one leak is in one horizontal direction the unbalance force of the other load will be in the opposite horizontal direction, synchronizing means co; prising a control circuit, and switches in the on cuit that synchronously close only in response to the direction of the unbalance forces that is other than the selected ut-oi-phase value, responsive to the energization of the control circuit for temporarily opening the motor armature circuit of the motor leading by more than the selected out-of-phase value, and means for controlling the interval the motor is deenergized as a function of the angle of lead.

4. In a system of control, in comoination, a motor operating a relatively heavy reciprocatory load back and forth in a horizontal direction, a similar motor operating a similar load back and forth in a horizontal direction that is parallel to the direction of operation of the load operated by the first motor, and means for briefly deenergizing the motor operating at a slightly higher speed at an instant when its load changes in direction from a direction that is opposite to the direction of movement of the load of the other motor to a direction that is the same as the direction of movement of the load of the other motor.

5. In a system of control, in combination, a motor operating a relatively heavy reciprocatory load back and forth in a horizontal direction, a similar motor operating a similar load back and forth in a horizontal direction that is parallel to the direction of operation of the load operated by the first motor, means for briefly deenergizing the motor operating at a slightly higher speed at an instant when its load changes in direction from a direction that is opposite to the direction of movement of the load of the other motor to a dir ction that is the same as the direction of movement of the load of the other motor, and means for controlling the period of deenergization as a function of the time period the loads move in the same direction.

6. In an industrial application where a large number of like motors separately operate an equal number of like relatively heavy reciprocatory loads at about the same speed of means for operating the motors in pairs, preferably adjacent or aligned pairs, such that when one load of one motor moves in one horizontal direction the load of the other motor will move in an opposite horizontal direction in combination, a control circuit, switching means that close said circuit when one load has moved beyond its extreme position in one direction and is returning while the other load has not yet arrived at its opposite extreme position, and means for decreasing the energy supplied to the motor driving the leading load by the energization of the control circuit.

'7. In an industrial application where a large number of like motors separately operate an equal number of like relatively heavy reciprocatory loads at about the same speed of means for operating the motors in pairs, preferably adjacent or aligned pairs, such that when one load of one meter moves in one horizontal direction the load of the other motor will move in an opposite horizontal direction, in combination, a control circuit, switching means that close said circuit when one load has moved beyond its extreme position in one direction and is returning while the other load has not yet arrived at its opposite extreme position, means, operable by the energization of the control circuit, for decreasing the energy supply for a relatively short time interval of the motor driving the leading load, and means for controlling the length of said time interval as a function of the magnitude of the lead of the leading load.

FREDERICK D. SNYDER.

No references cited. 

